This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This is a new grant to explore the role of serotonin in mediating stress induced infertility. Female cynomolgus monkeys, which like women, have 28-day menstrual cycles throughout the year, show individual differences in responsiveness to stress, with stress-sensitive animals rapidly developing stress-induced reproductive dysfunction, and stress-resilient animals maintaining normal menstrual cyclicity throughout stress exposure. The stress used for these studies is patterned after that documented in women with Functional Hypothalamic Amenorrhea (FHA;a clinical condition which accounts for as much as 30% of female infertility) in which monkeys are exposed to a mild psychological stress (moving to a new room) and a moderate metabolic stress (a 20% decrease in calorie intake and moderate running for an hour a day, 5 days a week). To date, we have studied monkeys in non-stressed conditions. We found that stress-sensitive monkeys have lower physiological release of serotonin, a down regulation of function in the central serotonergic system [as indicated by lower tryptophan hydroxylase (THP) 2 gene expression, less serotonin transporter (SERT) gene expression, less 5HT-1A receptor gene expression, and less expression of genes degrading serotonin (MAO-A and MAO-B)], as well as an up-regulation of 5HT2A and 2C receptors in the hypothalamus, compared to more stress-resilient animals. We have preliminary data showing that treatment of stress-sensitive monkeys in a nonstressed condition with a serotonin reuptake inhibitor (SSRI) increases reproductive hormone secretion in a normal menstrual cycle.